A young girl looks out of her car window as crews work to clear the massive pileup on Interstate 90 in Leroy Township, Ohio, on Dec. 24, 2013. / Jeff Forman, AP

by Larry Copeland and Paul Overberg, USA TODAY

by Larry Copeland and Paul Overberg, USA TODAY

A harsh winter raking the nation with waves of storms is spawning a huge toll in highway pileups, the out-of-nowhere chain-reaction crashes that can turn a snowy or icy highway into a mile-long junkyard in minutes.

Since Dec. 1, a USA TODAY analysis shows police have reported at least 42 pileups with at least 10 vehicles, or at least five vehicles when someone was killed. That's a rate of almost one per day.

One of the most recent occurred last week â?? a 46-vehicle crash near Michigan City, Ind., Thursday that killed three, injured more than 20 and left some lanes of Interstate 94 still closed into the next day. Police said drivers hit by a sudden snow whiteout did not slow enough for conditions.

For all of 2013, at least 107 pileups occurred on U.S. roads, or about two a week. But they cluster in winter â?? fully a third happened in January, February and December.

That's when drivers are most likely to suddenly face blinding conditions, especially an unexpected snow squall in the Midwest and Northeast. But dust storms in the West and mountain fog in the Southeast can produce the same results. In 2013, USA TODAY found some kind of adverse weather conditions present during 62% of pileups.

Experts point out a common ingredient: People driving too fast for conditions.

"Visibility is usually pretty poor when these crashes occur," said William Van Tassel, manager of driver training programs for auto club AAA. "Assume that the road is blocked just beyond the point where you can't see. Then you can adjust your speed accordingly."

"People need to keep in mind that the posted speed limit is for optimal driving conditions," said Fran McLaughlin, director of support services for the Milwaukee County, Wis., Sheriff's Office. "If you have wet, icy or snowy roads, we ask that people drive defensively. They need to allow more stopping distance. They need to slow down."

Last month a Wisconsin traffic camera caught a pileup as it began, creating a video that went viral when it was released by the state Department of Transportation. It opens with three lanes of heavy traffic moving slowly in heavy snow. A couple cars, moving much faster, skid, collide and block the road. More too-fast vehicles arrive and a pileup mushrooms within seconds. Police estimate more than 70 vehicles were involved.

Pileups don't often kill anyone, but they usually leave a trail of injuries, medical bills, lost wages and damaged vehicles and paperwork that can last for years. The average roadway fatality costs about $1.32 million in associated economic costs and the average crash with a critically injured survivor costs about $1.5 million, based on a 2002 National Highway Traffic Safety Administration calculation adjusted for today's dollars. More recently, in 2011, AAA concluded â?? after analyzing the financial toll of traffic crashes in 99 cities â?? that a fatal crash costs about $6 million and an injury-only crash $126,000.

About three-quarters of the pileups in 2013 occurred on interstate highways or similar roads,such as New Jersey's Garden State Parkway. Experts say that makes sense since this kind of kind of massive conflagration is fueled by lots of traffic moving at fairly rapid speed.

One of the interstate pileups â?? the largest crash in Ohio history -- occurred shortly before noon on Jan. 21, 2013, on Interstate 275 just north of Cincinnati. The crash involved 86 vehicles. A 12-year-old girl was struck and killed by a median safety cable after she got out of a crashed vehicle, said Jim Knapp of the Hamilton County Sheriff's Office.

Sixteen investigators tried to determine what caused the crash, which closed the interstate for more than five hours, Knapp said. They interviewed witnesses, photographed the scene, did accident reconstruction. It fell to one officer to keep track of which vehicle was towed by which wrecker.

In the end, police compiled a 258-page investigative report and determined that no one was at fault. "We were trying to find out exactly what happened," Knapp said. "In the end, it wasn't possible. We had a whiteout condition. People were driving on the expressway. A snowstorm blew across that part of the expressway. It started with two or three or four cars, and just multiplied from there."

"Nobody was found at fault," he said. "There was no law broken. With the first two or three or four people, it was just impossible to tell who made a mistake."

It can sometimes be just as difficult for auto insurers to determine who's liable in multiple-vehicle pileups, said Dave Eaton, auto claim consultant with insurer State Farm. Claims investigators usually do their own investigation after the police complete theirs â?? which can mean lengthy delays in difficult-to-untangle chain-reaction crashes. "It can be impossible to determine what happened," Eaton said.

Following their investigation, insurers might determine that a 50-vehicle pileup was actually 10 or 12 separate accidents, with liability in each. In some crashes in certain states, liability can be divided among drivers based on claims investigators' determination of their share of fault, Eaton said.

USA TODAY's analysis found that icy roads were a factor in 15 pileups last year and snow or freezing rain in another nine. In all, wintry weather accounted for about 40% of pileups.

Among other weather conditions, fog accounted for nine crashes. These are often worst in the Southeast, especially in the mountains. The worst such crash in 2013 involved 95 vehicles. It occurred March 31 in Virginia on Interstate 77 near its interchange with the Blue Ridge Parkway, just north of the North Carolina state line.

Dust storms were a factor in at least six pileups in 2013, typically in the Southwest. These dust storms are usually fall into one of three categories, according to Ken Waters, a warning coordination meteorologist in the National Weather Service's Phoenix office who has studied traffic crashes caused by dust storms. They are: huge clouds of dust generated by monsoon thunderstorms in the summer, dust storms caused by large-scale cold fronts in late winter and early spring, and the most problematic, very small scale, localized dust events that Waters calls "ribbons of dust."

"These are very, very difficult for meteorologists to predict," Waters said. "They are the most likely to surprise people. With the other two types, we can give a heads-up. From a motorist's standpoint, they often turn out to be a huge surprise."

Waters said that's what happened on Oct. 29, 2013 at Pichaco Peak on Interstate 10 between Phoenix and Tucson, where 19 vehicles were involved in a chain reaction crash that killed three people and injured 12.

According to Van Tassel with AAA, most drivers in chain-reaction crashes make one or both of two errors. "They're driving too fast for conditions, and-or they're not maintaining enough space around their vehicle," he said. "Normally, you want to stay 3-4 seconds behind the car in front of you in clear, dry conditions. In these (icy) conditions, you want 5 or 6 or more seconds that give you time to respond."

However, he said, even that might not be enough. "You could everything right and still get pushed into the vehicle in front of you," Van Tassel said. "The big question is, 'Do you stay in the car or do you get out?' The answer is, 'It depends.' It depends on the environment, what else is going on around you. If another car is approaching and going to plow into you, it's better to be in the car belted than to be outside the car. But if no other cars are approaching, it's safer to get out of the car and find a safe location."

But Van Tassel acknowledged: "There's no zero-risk option here."

The historic Ohio crash last January highlights the dilemma motorists often face. The 12-year-old girl who was killed, Sammy Reagan, had gotten out of the vehicle in which she was riding. Knapp said that might not have been a good idea. But he said investigators walking along the line of crashed vehicles found two cars - crushed under trucks - that were missed in an initial survey. The occupants had gotten out of those vehicles.

"For them it was a good idea to get out," he said. "That's a decision that each person has to make."